Hydroxy substituted arylophenone derivatives are commercially useful in synthetic plastics. For example, 4,4'-dihydroxybenzophenones are useful as monomers in the production of epoxy and polycarbonate resins. See, e.g., Lysenko et al., Electrocatalytic Method for Producing Dihydroxybenzophenones, U.S. Pat. No. 4,624,758 (Nov. 25, 1986). Epoxy resins useful in coatings, adhesives and casting resins are made by reacting a bisphenol, such as a 4,4'-dihydroxybenzophenone, with an epihalohydrin. Polycarbonate resins useful in coatings and casting resins are made by reacting a bisphenol and phosgene.
The method of producing dihydroxybenzophenones taught by Lysenko et al. includes the electrocatalytic oxidation of bis(4-hydroxyphenyl)methanes using a 2,3-diohloro-5,6-dicyano-1,4-benzoquinone oxidation catalyst. Although the process works well, the oxidation catalyst is not commercially available in large quantities and the process requires electricity, an expensive raw material.
European Patent No. 69,598 issued to Dahl et al. teaches production of hydroxy substituted arylophenones by reacting phenol with hydroxy substituted aryl acid halides or hydroxy substituted aryl carboxylic acids and esters thereof. The reaction takes place in the presence of a Lewis acid catalyst, such as boron trifluoride, and a strong acid.
Other methods are known for producing hydroxy substituted arylophenones. For example, Rose et al., Production of Dihydroxy Arylophenones, U.S. Pat. No. 4,433,172 (Feb. 21, 1984), teach the production of hydroxy substituted arylophenones by reacting diaryl carbonates with fluoroalkanesulfonic acids. Japanese Patent JP 5,901,438 (January 6, 1984), teaches the production of 4,4'-dihydroxybenzophenone by a two step process. In step one, a bis(4-trichloromethylphenyl)carbonate is reacted with phenol in the presence of a Lewis acid catalyst to produce a 4,4'-(4-hydroxybenzoyl)phenyl carbonate intermediate. This intermediate is subjected to alkali hydrolysis in a second step to produce the desired benzophenone. Stanley teaches, in Process of Preparing Hydroxy-Alkoxy Arylophenones, U.S. Pat. No. 3,073,866 (Jan. 15, 1963), production of hydroxy and alkoxy substituted arylophenones by condensing a hydroxy aryl carboxylic acid with an alkyl ether of phenol in the presence of phosphorous trichloride, zinc chloride, and a phosphoric acid solvent.
As can be seen, a need exists for a method capable of producing commercial quantities of hydroxy substituted arylophenones economically and at a reasonably high yield.